PVK-2B-505-N-4191B Nachi Piston Pump 50.5cc 350bar

Product Overview

The PVK-2B-505-N-4191B and PVK-2B-505-N-4962F are Nachi-Fujikoshi PVK Series swashplate-type axial piston variable displacement pumps. The PVK Series is Nachi’s compact variable pump line for small excavator hydraulic systems, covering PVK-0B, PVK-1B, and PVK-2B sizes for 1.5–2 ton, 2.5–3.5 ton, and 4–5 ton class excavators respectively. The PVK-2B-505 is the flagship model of the series, delivering a maximum displacement of 50.5 cm³/rev.

The PVK-2B-505 Series features a swashplate axial piston design with Constant Power Control and Load Sensing functionality. The constant power control enables the pump to automatically adjust output based on operating conditions, fully utilizing engine power while preventing overload and improving fuel efficiency. The compact design allows installation in space-constrained engine compartments.

The PVK-2B-505-N-4191B and PVK-2B-505-N-4962F are OEM variant models within the Nachi PVK-2B-505 series. They share identical displacement, pressure ratings, and speed ranges—the primary difference lies in the suffix codes, which correspond to different OEM assembly configurations and application specifications.

As a direct OEM-equivalent replacement solution for the Nachi PVK Series, this product offers complete in-situ interchangeability, strictly adhering to Nachi’s original design specifications and mounting interface standards. Every unit undergoes 100% simulated duty-cycle testing, ensuring that key performance metrics—including volumetric efficiency, pressure-flow characteristics, and case drain flow at rated pressure and full displacement—meet or exceed original factory specifications.

Technical Specifications (Bulleted List)

• Model Numbers: PVK-2B-505-N-4191B / PVK-2B-505-N-4962F

• Brand Series: Nachi-Fujikoshi PVK Series

• Pump Type: Swashplate Axial Piston Variable Displacement Pump

• Maximum Displacement: 50.5 cm³/rev (3.08 in³/rev)

• Nominal Pressure: 34.3 MPa (350 kgf/cm² ≈ 350 bar)

• Maximum Peak Pressure: 39.2 MPa (400 kgf/cm² ≈ 400 bar)

• Rated Speed: 2200 rpm

• Maximum Speed: 2500 rpm

• Control Type: Constant Power Control + Load Sensing

• Power Regulator: Built-in (Constant Horsepower Control)

• Mounting Type: Flange Mounting (Compact Design)

• Housing Material: Cast Iron

• Hydraulic Fluid: Mineral Oil

• Operating Temperature Range: 30–90°C

• Applicable Excavator Class: 4–5 ton

• Weight: Approx. 35 kg

• OEM Equivalents:

  • PVK-2B-505-N-4191B — Fits Yuchai YC55, etc.

  • PVK-2B-505-N-4962F — Fits Hitachi ZX48, etc.

Key Technical Advantages

1. Constant Power Control + Load Sensing for Optimal Engine Utilization
The PVK-2B-505 Series features Constant Power Control with Load Sensing functionality. Constant power control enables the pump to automatically adjust output based on operating conditions, automatically matching engine output power to prevent overload and energy loss; load sensing regulates flow based on system load demand for on-demand oil supply. Working together, they improve operational speed while reducing fuel consumption.

2. Compact Design for Space-Constrained Engine Compartments
The PVK-2B-505 features a compact design that fits into space-constrained engine compartments. This makes it particularly suitable for 4–5 ton class mini excavators, where engine bay space is extremely limited and pump dimensions are critical.

3. 350 bar High-Pressure Rating for Heavy-Duty Small Excavator Applications
The PVK-2B-505 delivers a nominal pressure of 34.3 MPa (350 bar) with peak pressures up to 39.2 MPa (400 bar) . At 50.5 cm³/rev displacement with 2200–2500 rpm speeds, it outputs ample hydraulic power for heavy-duty excavating, breaking, and other demanding small excavator applications.

4. Built-in Gear Pump for Stable Pilot Control Oil Supply
The PVK-2B-505 Series is standard-equipped with a gear pump for pilot control operation, providing a stable hydraulic source for the small excavator’s pilot control system. This integrated design simplifies system layout, reducing installation space requirements and system costs.

5. Broad Application Coverage for Global Market Compatibility
The PVK-2B-505 Series is widely compatible with Hitachi, Yuchai, Komatsu, and other 4–6 ton class mini excavators. Compatible models include: Hitachi ZX40U-2/ZX40U-3/ZX50U-2/ZX50U-3/ZAX55/ZAXIS55/ZX55, Yuchai YC55/YC60, and Komatsu EX30/PC40-7.

Application Areas

• Small Excavators (Primary Application): Yuchai YC55, Yuchai YC60

• Hitachi Mini Excavators: ZX40U-2, ZX40U-3, ZX50U-2, ZX50U-3, ZAX55, ZAXIS55, ZX55

• Komatsu Mini Excavators: EX30, PC40-7

• Other 4–6 Ton Class Mini Excavators: Kaiyuan 55/60, Nante 60, and other domestic models

Expert Maintenance Tips

1. Model Confirmation & Pre-Installation Inspection: Prior to installation, confirm the complete model code—PVK-2B-505-N-4191B or PVK-2B-505-N-4962F. Although they belong to the same series, the suffix codes correspond to different OEM assembly configurations. Verify that the mounting flange specification and splined shaft type match the host machine PTO interface. Manually rotate the shaft before installation to confirm smooth, obstruction-free rotation.

2. Fluid Cleanliness Control: Use high-quality hydraulic oil meeting Nachi specifications. A minimum filtration rating of ISO 18/15 is recommended. Complete system flushing is mandatory before initial start-up. The built-in gear pump is equally sensitive to fluid cleanliness—oil drawn by the gear pump flows directly into the pilot control system, and any contamination will affect pilot control reliability.

3. Constant Power Controller Tuning: The PVK-2B-505 Series features a built-in constant power controller. The constant power setting determines the pump’s power output characteristics under different operating conditions. During commissioning, set according to the engine’s rated power to fully utilize engine efficiency without overload or speed drop. Perform initial settings under no-load conditions, then gradually increase load to target operating conditions with fine adjustments.

4. Initial Start-Up & Priming: Before first start-up, pre-lubricate the pump by filling the housing with clean hydraulic fluid through the case drain port. Perform a brief jog start (5–10 seconds) to check for abnormal noise, leakage, or excessive vibration. Then start the pump and run at low load for several minutes to purge air from the pump and system lines.

5. Case Drain Port Positioning & Pressure Monitoring: During installation, ensure the drain port is positioned higher than the pump body to prevent oil starvation in the pump chamber after shutdown. The PVK-2B-505 Series is designed for 4–5 ton class mini excavators—the compact installation space requires drain line routing to avoid kinks or compression, ensuring unobstructed drainage.

6. Scheduled Maintenance & Filter Replacement: Follow the maintenance intervals specified in the Nachi PVK Series service manual. Pay particular attention to filter condition, fluid cleanliness, and seal integrity during routine inspections. Regular hydraulic fluid and filter replacement is essential for long-term reliable pump operation. The PVK-2B-505 Series’ compact design means its internal rotating components are more, demanding higher maintenance quality.